(i) Field of the Invention
This invention relates to a display device for displaying a tomographic image used for diagnosis and to a displaying process.
(ii) Description of the Prior Art
For diagnosis using a two-dimensional medical image such as an x-ray CT (computed tomography) image, an MRI, an angioimage and angiographic image, a film viewer using a backlight called a Schaukasten has been used after printing the image on a film.
In X-ray CT, a helical CT device has been frequently used, where a patient is helically scanned for collecting data while continuously rotating an X-ray light and moving the patient on a platform in a given rate. More recently, a helical scanning procedure has been using a multi-slice CT device where a plurality of detectors are aligned to simultaneously collect data for multiple slices during one rotation.
Such advance in technology has achieved extension of a scanning range, reduction in a testing time and improvement in resolution along a body axis. For example, a CT image with a 0.5 mm pitch has been able to be obtained in multi-slice CT and thus 900 pieces of CT images can be obtained in a short time when scanning 45 cm of a body. However, it has led to an enormous amount of data, taking a considerably long time for reading each image using a Schaukasten and resulting in a huge number of films. For reducing the number of films, there has been an attempt that the number of cuts (i.e., slice images ) printed on one film (size: 35×43 cm) is increased to about 20 images. It, however, leads to reduction in size for one image , causing it difficult to read the image. There is, therefore, a limit in reduction in the number of films.
In addition, display devices for a CT image are known, in which many CT images can be displayed on a display such as a CRT using a computer not only as a 2D (two-dimensional) image but also as a 3D (three-dimensional) image. Some of these display devices have pager function that each of a plurality of CT images (hereinafter, a “CT image” refers to, unless otherwise indicated, a 2D image.) is displayed one slice by one slice in the manner of paging by manual or automatical operation. It has an advantage that more CT images can be compactly read compared with “Schaukasten”, because it can eliminate the need for handling many films.
A device displaying a 2D or 3D image is manufactured and marketed by multiple manufactures. These devices are mainly operated by keyboard input and selection/operation in a display device using a mouse because the system utilizes a fixed hardware (a family such as MAC and DOS/V) for the purpose of universality in a software. To date, a variety of softwares allows us to display a 2D image, 3D image or a plurality of images by dividing a screen.
However, when an operator is intensely reading images on a screen by actually using such a universal system, it gives much stress to the operator to do key input from a keyboard or to select an event by clicking an icon indicated on a screen using a mouse. This is because operator's viewing points disperses two or more points. If a display device is used only as a viewer having pager function which shows in the manner of paging CT images (two-dimensional images), a computer compliant to 3D image displaying function may be of overspecification as a hardware, leading to a higher cost.
Thus, when a very technical operation such as reading a CT image (i.e., observing images for medical examination) is required, that is, when the results are very important and it is also needed to acquire the results as readily as possible, a universal system utilizing software is rather inferior in operability and may interfere concentration of the operator for intense image-reading.
In terms of softwares in a conventional display device for a CT image, there are display devices which can display a series of CT images in the manner of paging or display two or more static images, but there are no display devices which can display two series of CT images simultaneously in the manner of paging and there are no software dealing with such operation.